244 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 1. 
MINERALOGY AND LITHOLOGY. 
PLATE VI. 
Incipient alteration of andalusite, as seen in a basal section—page 106. 
Complete alteration of andalusite into cyanite, as seen in a basal sec- 
tion—page 106. 
Microscopic cavities as seen in a section of the olivine diabase from 
Campton falls. The walls are coated with sphzrosiderite, and prisms 
of calcite project into the cavities which, with this exception, are full 
of analcite—page 112. 
Apatite needles, as seen in a section of diabase from Bemis brook— 
pages 123 and 152. 
The structure of the crystalline grains which constitute ordinary lime- 
stones, as seen in thin sections between crossed Nicol prisms— 
page 128. 
Cavities common in the quartz of porphyries and granitic rocks, pages 
181 and 192,—very highly magnified. 
PLATE VII. 
Augite in a section of augite sienite from Jackson. Alteration into horn- 
blende is seen in progress, and the cleavages in the altered and unal- 
tered portions bear the same relationship to one another as do the 
prisms of augite and hornblende if constructed upon the same clino- 
diagonal—pages 57 and 206. 
Section of hornblende schist from Cornish, showing the pleochroism of 
the hornblende—pages 16 and 61. 
A crystal of hornblende in a section of eruptive diorite from near the 
Profile house. The form of the crystal is mostly filled with an aggre- 
gate of magnetite, biotite, and calcite—pages 66 and 163. 
Crystals of olivine in a section of the olivine diabase from Campton 
falls. The crystals are wholly altered into serpentine—pages 71 and 
157. 
A garnet in a section of staurolite slate, showing the progress of an al- 
teration into chlorite—page 75. 
A basal section of oligoclase from the Antrim granite. The section is 
so placed, between crossed Nicol prisms, that one set of its twin lam- 
ine is dark—page 88. 
PLATE VIII. 
Orthoclase as seen in a section of the Chocorua granite, with polarized 
light, showing the interlamination of two parts, in which the optical 
constants are differently arranged—page Ior. 
X 50 
X 50 
X 30 
x 100 
x 30 
X 30 
Xx 30 
x 30 
xX 30 
X 30 
x 30 
X 50 
